Generally described, computing devices and communication networks can be utilized to exchange information. In a common application, a computing device can request content from another computing device via the communication network. For example, a user at a personal computing device can utilize a software application process, typically referred to as a browser, to request a Web page from a server computing device via the Internet. In such embodiments, the user computing device can be referred to as a client computing device, and the server computing device can be referred to as a content provider.
Once the client computing device obtains the Web page, the content may be processed in a number of stages by the software browser application or other client computing device interface. For example, the browser may parse the Web page to process various Hypertext Markup Language (“HTML”) layout information and references to associated resources, may identify and process Cascading Style Sheets (“CSS”) information, may process various scripts associated with the Web page, may construct a native object model to represent one or more components of the Web page, and may calculate various layout and display properties of the processed content for presentation to a user.
From the perspective of a user utilizing a client computing device, a user experience can be defined in terms of the performance and latencies associated with obtaining a Web page, processing embedded resource identifiers, executing script files, and rendering content on the client computing device. Latencies and performance limitations of any of the above processes may diminish the user experience. Additionally, latencies and inefficiencies may be especially apparent on computing devices such as netbooks, tablets, smartphones, and the like, which may have limited resources in terms of processing power, memory, or network connectivity.